This invention relates to a pipe ending machine, particularly controlling accurately bending action with high speed by means of a ball threaded rod and a ball threaded nut.
Conventional pipe bending machines uses air or oil pressure cylinders or motors as power source for bending straight pipes into preset angles. Air pressure cylinders have a drawback of leak in use, and oil pressure cylinders may easily leak oil and have oil temperature problems. In general, air or oil pressure cylinders used as power source involves bad stability in bending process, so motors are preferable for pipe bending machines. However, pipe-bending machines using motors as power source still may be influenced by counter-pressure of the component such as a speed reducer, causing accuracy hard to ensure.
A pipe-bending machine disclosed in U.S. Pat. No. 4,750,346 is shown in FIGS. 1 and 2, bending a pipe 10 to form a bent portion 101, including a base 11 laid on the ground, a material feeding device 12 fixed on the base 11 for moving a pipe 10. The feeding device 12 has a clamp head 13 in the front portion, a bending device 14 fixed at the most front (in the left side in FIG. 1) to form a bent portion 101. The bending device 14 has an arm-turning shaft 141 for the pipe 10 to rest on, and a turning arm 142 to hold the pipe 10. A clamp mold 143 to clamp the pipe 10 is fixed on the turning arm 142, which is moved by a transmitting device 2 deposited in a lower portion of the base 10.
As shown in FIGS. 2 and 3, the above patent has the transmitting device including a speed reducer 21 fixed in a lower portion of the base 11 and a motor 22 under the speed reducer 21 to move together. The speed reducer 21 has an output shaft 211 protruding up an upper side and in parallel with the axis of the arm-turning shaft 141. A disc 212 is fixed on the output shaft 211 to move together, and two cranks 23 are connected between the disc 212 and the turning arm 142. When the motor 22 drives the speed reducer 21, the output shaft 211 transmits power to turn the disc 212, and then the cranks 23 to force the turning arm 142 rotate with the arm-turning shaft 141 as a pivot. Then the pipe 10 clamped between the clamp mold 143 and the arm-turning shaft 141 is bent to form the bent portion 101.
The conventional pipe-bending machine 1 utilizes the motor 22 and the speed reducer 21 to directly move the two cranks 23, and then rotates the turning arm 142 to achieve the objective to bend a pipe. But a common speed reducer 21 may produce counter-pressure problem owing to accuracy of a component in the process of operation. In order to enhance accuracy of high speed bending, a low counter-pressure (or good process accuracy) speed reducer may be chosen, but this kind of speed reducer must have its gears to be coordinated with cutting, grinding, hardening, choosing and assembly. Manufacturing may cost very high, and take much time. If a speed reducer 21 of common counter-pressure is used in a pipe bending machine, error in counter-pressure is directly transmitted by the two cranks 23 to the turning arm 142, letting the arm-turning shaft 141 also have the same counter-pressure to cause inaccuracy in pipe bending action with high speed. Besides, the two cranks 23 are designed to interact with each other, the speed reducer and the motor 22 have to positioned vertical, so the height of the base 11 has to be increased, with the dimensions of the pipe bending machine difficult to reduce.